Rolex TRU-BEAT ref 6556 yellow gold, 1955 Movement and functions Automatic cal. 1040 "dead beat" seconds Case 18 kt yellow gold with screw back case, 35mm Dial Silvered with gold applied long baton indexes and hands Features Launched in 1954, The Rolex Tru-Beat reference 6556 was created for doctors to allow a more accurate readings of patients' pulse rates. Housing the caliber 1040, this the only one Rolex watch equipped of a "dead-beat" second mechanism that advances the seconds hand only once per second. The present model date from 1955 and is preserved in excellent original conditions with a very sought-after silver dial and one of the very few cases produced in 18 kt gold for this reference. Tru–Beat 18 ref 6556, 18 kt gold case n.139xxx 1955. Case, dial, movement signed.